1. Field of the Invention
This invention relates in general to a submersible centrifugal pumps, and in particular to wear resistant elements in the pump stages for reducing abrasion.
2. Description of the Prior Art
A submersible centrifugal pump includes a downhole electric motor coupled to a centrifugal pump. The pump has numerous stages of diffusers and impellers that pump fluid to the surface from the well. Normally the impellers and diffusers are made from a cast alloy. The impellers rotate within the diffusers, and the mating sliding surfaces are machined smooth to reduce wear and to provide close clearances for sealing. Thrust washers may be located between the impellers and diffusers to accommodate downward and upward thrust.
While these types of pumps are successful, if the fluid being pumped contains a significant amount of entrained sand, the abrasive particles will abrade and/or erode the pump impellers and diffusers, shortening the lift of the pump. Normally, a pump needs to be pulled from the well for servicing only every twelve to eighteen months. If the sand has abraded the pump components severely, the pump might have to be pulled earlier than the normal life. The cost for pulling the pump, including lost production time, can be quite expensive, particularly with offshore wells.
U.S. Pat. Nos. 4,678,399, Vandevier et al, July 7, 1987, and 4,511,307, Drake, Apr. 16, 1985, show inserts that are attached to the impeller and diffuser. These inserts are harder than the other portions of the impeller and diffuser to combat wear.